Dendritic cells are constantly sampling the lumen of the intestines for harmful bacterial. Once they find a threat, they migrate to the neighboring lymph nodes to activate T cells. Since our intestines contain hundreds of millions of bacterial cells, dendritic cells have developed to ignore the commensal bacteria that would not harm us. This “ignorance” or tolerance has proved essential for intestinal health. Breakdown of this tolerance results in inflammatory bowel diseases or IBD. We have previously written about how defective dendritic cells are to blame for the initiation of IBD.